Sensors including integrated circuits (ICs) that directly sense the physical properties of objects in the sensor's environment have come into widespread use in electronic equipment. These ICs are desirably in close proximity to the external environments they measure, but they should not be damaged by the mechanical and/or electrical events that an external environment can apply.
One type of such sensing is finger sensing and associated matching that have become a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes.
A particularly advantageous approach to fingerprint sensing is disclosed in U.S. Pat. Nos. 5,963,679 and 6,259,804, assigned to the assignee of the present invention, the entire contents of which are incorporated herein by reference. The fingerprint sensor is an integrated circuit sensor that drives the user's finger with an electric field signal and senses the electric field with an array of electric field sensing pixels on the integrated circuit substrate. Additional finger sensing integrated circuits and methods are disclosed in U.S. Patent Application Publication No. 2005/0089202 entitled “Multi-biometric finger sensor including electric field sensing pixels and associated methods”, also assigned to the assignee of the present invention, and the entire contents of which are incorporated herein by reference.
A number of prior art references disclose various types of packaging of IC sensors. For example, U.S. Pat. No. 6,646,316 to Wu et al. discloses an optical sensor including a sensing die with bond pads on an upper surface thereof. A flexible circuit board is coupled to the bond pads, and has an opening over the sensing surface.
U.S. Pat. No. 6,950,541, assigned to the assignee of the present application, discloses a fingerprint sensor package that includes a fingerprint sensing integrated circuit. The fingerprint sensor package is carried in a housing. The fingerprint sensor and the housing are carried by a flexible circuit substrate.
U.S. Patent Application Publication No. 2007/0086630, also assigned to the assignee of the present invention, discloses a finger sensor including a finger sensing integrated circuit carried by a flexible circuit. A frame surrounds the finger sensor.
Unfortunately, prior fabrication processes manually attached a separate protection housing or frame late in the assembly process that protects the fingerprint or finger sensing integrated circuit. In many instances, the protection housing or frame is manually attached after the finger sensing integrated circuit has been coupled to the flexible circuit and is removed for installation into a device. In other words, the protection housing is not included as part of the finger sensor and flexible circuit substrate coupling process, but rather coupled manually prior to completion of a final fingerprint sensor package.
As a result of manually attaching a separate protection housing late in the assembly process, variances due to tolerances of the assembly would occur. For example, the protection housing may be manually coupled to be misaligned with the finger sensing integrated circuit and more particularly, the flexible circuit substrate. This may result in an increased amount of fingerprint sensor packages being rejected for quality and/or a reduced overall fingerprint sensor package quality.